Epidemiology of human West Nile virus infections in the European Union and European Union enlargement countries, 2010 to 2018

Abstract

Background West Nile virus (WNV) circulates in an enzootic cycle involving mosquitoes and birds; humans are accidental hosts. Aim We analysed human WNV infections reported between 2010 and 2018 to the European Centre for Disease Prevention and Control to better understand WNV epidemiology. Methods We describe probable and confirmed autochthonous human cases of WNV infection reported by European Union (EU) and EU enlargement countries. Cases with unknown clinical manifestation or with unknown place of infection at NUTS 3 or GAUL 1 level were excluded from analysis. Results From southern, eastern and western Europe, 3,849 WNV human infections and 379 deaths were reported. Most cases occurred between June and October. Two large outbreaks occurred, in 2010 (n = 391) and in 2018 (n = 1,993). The outbreak in 2018 was larger than in all previous years and the first cases were reported unusually early. The number of newly affected areas (n = 45) was higher in 2018 than in previous years suggesting wider spread of WNV. Conclusion Real-time surveillance of WNV infections is key to ensuring that clinicians and public health authorities receive early warning about the occurrence of cases and potential unusual seasonal patterns. Human cases may appear shortly after first detection of animal cases. Therefore, public health authorities should develop preparedness plans before the occurrence of human or animal WNV infections.

West Nile and Usutu Virus Introduction via Migratory Birds: A Retrospective Analysis in Italy

“…In 2010, the eco-climatic conditions in Central European and Mediterranean countries promoted an intensive viral circulation resulted in the transmission of WNV to humans [58]. Outbreaks were reported in Greece, Romania, Hungary, Italy, Portugal, Spain, Russia, and EU neighboring countries, such as Israel and Turkey, becoming, as a matter of fact, the most widely spread arbovirus in the old continent [11,59]. Then, since 2018 with the first detection of WNV lineage 2 in Germany, this virus has been spreading towards northern Europe to the Netherlands in 2020 [60] and again in southern France in 2018 [61] and Spain in 2020 [62].…”

West Nile Virus Occurrence and Ecological Niche Modeling in Wild Bird Species and Mosquito Vectors: An Active Surveillance Program in the Peloponnese Region of Greece

“…Human infections follow a seasonal pattern, usually from early summer to early autumn [ 26 ] and are favored by climatic conditions. Increased ambient temperatures during summer [ 27 , 28 , 29 ], high precipitation in late winter/early spring [ 28 ] and summer drought [ 28 ] play an important role in virus epidemiology.…”

Experimental Evolution of West Nile Virus at Higher Temperatures Facilitates Broad Adaptation and Increased Genetic Diversity

“…Since its emergence in 1999, there have been approximately 52,000 WN human cases diagnosed in the U.S., resulting in over 2300 fatalities [ 4 ]. WNV lineage 2 has also risen in prevalence in Europe, with an increasing frequency of outbreaks in recent years [ 5 ]. WNV is predominately vectored by Culex mosquitoes, which are widely distributed, found in temperate regions of Europe, Asia, Africa, Australia, and North, Central, and South America [ 6 , 7 , 8 , 9 ].…”